Queensland farmers and activists have applied for a review of what they call a "scientifically flawed" decision to grant a water licence to New Hope's major thermal coal mine at New Acland the state's south.
Stage three of the open-cut mine northwest of Toowoomba was granted a water licence in October, clearing the final hurdle for work to start.
The project will lift New Acland's thermal coal output from 4.8 million tonnes to 7.5 million tonnes a year and extend its life for 12 years to 2034.
The Oakey Coal Action Alliance and Lock the Gate have applied for the decision to grant the licence to be reviewed because they say it was made without sufficient modelling of the mine's impacts on groundwater, or a clear plan to monitor and manage any impact.
Oakey Coal Action Alliance secretary Paul King says expert analysis indicates the water department has made a "shocking error of judgement".
"Farmers are seriously concerned that the Palaszczuk government has made a scientifically flawed decision and fear their livelihoods and ability to grow food for Queenslanders will suffer as a result," he told AAP on Monday.
"The Palaszczuk government should be prioritising farmers' water security over coal."
Granting the water licence ended a long political and legal battle to stop the project, but if the department refuses to consider or reject the application for a review it could return to the courts.
Under state law, either the Oakey Coal Action Alliance or Lock the Gate could apply to challenge the decision to grant the water licence in the Land Court.
New Acland doesn't use groundwater but farmers and activists are concerned mining will deplete groundwater in the aquifers beneath the pit.
The analysis commissioned by the two groups found "too much uncertainty" in the modelling used for New Hope's licence application and groundwater impact assessments had been delayed for 18 months.
Mr King said impacts should be understood before mining licences are granted, not after that fact.
Groundwater drawdown was likely underestimated as well, the analysis said, with predictions in modelling used by the department already failing to match with observed water levels.
The application assumed underground faults would be a barrier to water flow when they may be conduits, meaning the impact on surrounding water users such as dairy farmers could be also underestimated.
Mr King said there was also no clear mechanism to monitor groundwater drawdown or to work out if New Acland is to blame.
"New Acland stage three will impact nearby dairy farmers who rely on water bores for their businesses. Farmers fear these bores will deplete or dry up after the mine starts operating," he said.
"Given the risks to water from the Acland coal mine are not properly understood and can't be managed, the Palaszczuk government should prioritise Queensland's food and water security over coal."
